Adjustable pattern spray gun

ABSTRACT

A paint spray gun of the airless type is disclosed. The spray gun includes a spray tip having a non-circular, elongated sharp edged nozzle opening and also includes a chamber leading to and larger in area than the nozzle opening and a pre-orifice adjustable in area and positioned upstream from the chamber and co-axial with the nozzle opening. The disclosed pre-orifice is formed by arcuate recesses in opposed relatively movable jaws and, in its minimum area adjustment, is a non-circular elongated opening similar to the nozzle opening. Interfitting parts maintain the long dimensions of the nozzle opening and the preorifice in parallel relationship. When the area of the preorifice is adjusted to be in the range of not more than about twice to not less than about one-fourth the area of the nozzle opening, the liquid paint delivered under pressure to the gun passes from the pre-orifice through the chamber as a submerged jet and emerges from the nozzle opening to provide a uniformly atomized spray pattern with feathered edges. As the area of the pre-orifice is reduced through this range, the quantity of paint emitted is reduced without reduction of the velocity, permitting the spray pattern applied to the work to be narrowed without loss of quality or film thickness.

United States Patent [1 1 Levey et al.

[ Feb. 11, 1975 ADJUSTABLE PATTERN SPRAY GUN {75] Inventors: Gustave S.Levey, 6220 Reamer,

Houston. Tex. 77036; Edward Moser. Houston. Tex.

[73] Assignee: said Levey, by said Moser (22] Filed: Feb. 19, 1974 [211App]. No.: 443,480

[52] US. Cl 239/590.3, 239/526, 239/599 [51} Int. Cl B051) 1/04 [58]Field of Search 239/599, 597, 600, 601, 239/5903, 526, 583

[56] References Cited UNITED STATES PATENTS 3.000.576 9/1961 Levey etal. 239/597 X 3 5l5.355 (i/l970 Wagner 239/526 3.556.4ll l/l97l Nord eta] 239/599 X 3.659.787 5/1972 Ito 239/599 X Primary Examiner-M. HensonWood, Jr. Assistant E.ramt'ner--.lohn J. Love Attorney, Agent, orFirm-McNenny, Farrington, Pearne & Gordon [57] ABSTRACT A paint spraygun of the airless type is disclosed. The

spray gun includes a spray tip having a non-circular, elongated sharpedged nozzle opening and also includes a chamber leading to and largerin area than the nozzle opening and a pre-orifice adjustable in area andpositioned upstream from the chamber and coaxial with the nozzleopening. The disclosed preorifice is formed by arcuate recesses inopposed relatively movable jaws and, in its minimum area adjustment, isa non-circular elongated opening similar to the nozzle opening.lnterfitting parts maintain the long dimensions of the nozzle openingand the pre-orifice in parallel relationship. When the area of thepreorifice is adjusted to be in the range of not more than about twiceto not less than about one-fourth the area of the nozzle opening, theliquid paint delivered under pressure to the gun passes from thepre-orifice through the chamber as a submerged jet and emerges from thenozzle opening to provide a uniformly atomized spray pattern withfeathered edges. As the area of the pre-orilice is reduced through thisrange. the quantity of paint emitted is reduced without reduction of thevelocity, permitting the spray pattern applied to the work to benarrowed without loss of quality or film thickness.

40 Claims, 7 Drawing Figures ADJUSTABLE PATTERN SPRAY GUN BACKGROUND OFTHE INVENTION This invention relates to spray guns for liquids such aspaint or the like and, more particularly, to a spray gun forhydraulically atomizing the liquid to be sprayed.

In a hydraulically atomizing spray system or airless spray, the liquidis forced through a nozzle opening having sharp edges at sufficientlyhigh velocities to provide atomization of the liquid. The nozzle openinghas an elliptically shaped cross-section with sharp vertices to producean elliptical or oval shaped spray pattern.

The advantages of airless spraying are discussed in U.S. Pat. No.3,000,576 to Levey et al. In accordance with this prior patent, thenon-uniform spray pattern having thickened portions or pigtails whichhad therefore characterized airless spray techniques was eliminated bythe use of a restricted pre-orifice having a circular cross-sectiondisposed upstream from the spray tip nozzle opening.

The occurrence of such non-uniform spray patterns was associated withthe formation of a vena contracta upon acceleration of the liquid with alarge pressure drop through the nozzle opening which prevents fullatomization of the liquid at the vertices of the spray pattern. Theformation ofa harmful vena contracta was eliminated by accelerating theliquid with a large pressure drop through the restricted pre-orifice toprovide a submerged jet moving through the nozzle opening by its ownkinetic energy at substantially the same velocity. By controlling theliquid in this manner, a substantially uniform pressure and velocity wasobtained across the area of the nozzle opening, so that the liquid wasuniformly atomized and distributed across the spray pattern with auniform reduction in density or feathering at the margins of thepattern.

For purposes ofobtaining optimum atomization quality, thecross-sectional area of the pre-orifice opening should be substantiallyequal to the cross-sectional area of the nozzle opening of the spraytip. Satisfactory results are obtained so long as the area of thepre-orifice is not less than about one-fourth or more than about twicethe area of the nozzle opening. A number of variously sized, circularpre-orifices are presently required to accommodate the full commercialrange of spray tips in accordance with the teachings of the said U.S.Pat. No. 3,000,576. For use with seven different sized spray tips havingnozzle areas ranging from the equivalent ofa round opening with adiameter of 0.01 l of an inch to a round opening of 0.031 of an inch,eight different circular pre-orifices are currently marketed havingdiameters ranging from 0.012 of an inch to 0.039 of an inch, so thateach spray tip may be provided with a pre-orifice with an areasubstantially equal to or not exceeding twice the area of the nozzleopening. The changing of a pre-orifice may involve the disassembly of asignificant portion of the spray gun and, at least, results in aconsiderable loss of production time.

In some paint spraying applications, particularly in construction ormaintenance work, speed of application is paramount and quality ofatomization may be sacrificed for the maximum fan width applied asquickly as possible. To that end, the operator may forego the use of apre-orifice in order to obtain as wide a spray fan width as possiblesince it has been observed that the use of a pre-orifice will reduce thefan width and the volume delivered by as much as 10 percent to 15percent in an designated spray tip. After the faster rough applicationshave been applied. the op erator will necessarily expend valuableproduction time inserting an appropriate pre-orifice to obtain thequality atomization required for the areas or applications in whichquality is critical, and airless spraying without a pre-orifice isunsatisfactory.

SUMMARY OF THE INVENTION It has now been discovered that a non-circularpreorifice having a generally elongated cross-section can be utilized inan airless spray system employing a flat fan" or elliptically shapednozzle opening to provide a uniformly atomized spray pattern. Theelongated, major cross-sectional dimensions of the pre-orifice and thenozzle opening are maintained in substantially parallel relationship.Further, a pre-orifice having an adjustable cross-sectional area isprovided to permit corresponding variations in the spray fan and spraypattern of an airless spray gun.

In the illustrated embodiments, a pre-orifice assembly or capsuleprovides a restricted pre-orifice having a generally ellipticalcross-sectional configuration. The cross-sectional area ofthepre-orifice is adjustable, and it is defined by cooperating surfaces ofrelatively movable jaw members. The pre-orifice capsule includes springmeans for biasing the jaw members apart and cam following arms formoving the jaw members together upon the axial advance of a cammingmember disposed within the spray gun. The movement of the cammingmemeber is controlled by an external adjustment nut mounted on the spraygun. The preorifice capsule includes an axially projecting alignmentmember engaging the spray tip to coaxially align the nozzle opening andthe pre-orifice as well as to maintain the desired parallel relationbetween the major crosssectional dimensions.

The range of cross-sectional pre-orifice areas available is selected toaccommodate the conventional spray tip nozzle opening sizes which varyfrom an area equal to that of a circle of 0.01 l of an inch in diameterto an area equal to that of a circle of 0.035 of an inch in diameter.(For purposes of convenience, the nozzle opening and pre-orifice openingcrosssectional areas are hereinafter simply designated by the diameterin inches of a circle having an equal area.) More particularly, theelliptically shaped pre-orifice of the illustrated embodiment isadjustable from an equivalent area value of 0.01 l in its minimum areaposition to an equivalent area value of 0.035 in its maximum areaposition. In this manner, a single pre-orifice capsule may be adjustedto provide an optimum 111 area ratio between the pre-orifice opening andthe nozzle opening for the entire range of commercially avialable spraytip sizes.

In addition to providing the optimum 1:1 area ratio, the adjustablepre-orifice also provides area ratios substantially in excess of 2:1 formost of the spray tips commonly employed to enable an operator toachieve full spray fan angle width potential in high speed rough work bysimply adjusting the pre-orifice to its maximum size. Similarly, thespray fan angle may be narrowed or decreased for specific trim andfinishing applications by reducing the size of the pre-orifice. In bothof these cases, it it apparent that the volume delivcry and the spraypattern are adjusted without a significant loss of production time.

Thus, it has been discovered that the advantages and principles relatingto the use of a circular pre-orifice in an airless spray system asdisclosed in the aforementioned Levey et. al. patent can be obtainedwith a noncircular pre-orifice in accordance with the teachings of thesubject invention. This discovery has been utilized in providing apre-orifice having an adjustable crosssectional area which can bereadily incorporated into a conventional airless spray gun to attain theadvantages of using a pre-orifice while simultaneously eliminating theaforementioned prior art disadvantages of the same. Further, theprovision of an adjustable preorifice in an otherwise conventionalairless spray gun permits corresponding adjustments in the deliveryvolume and the spray pattern of the spray gun for resolving particularspraying problems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view of anairless spray gun provided with adjustable pre-orifice means inaccordance with the present invention;

FIG. 2 is a fragmentary, vertical section on an enlarged scale throughthe valve port and nozzle area portion of the spray gun shown in FIG. 1depicting the preorifice capsule and having parts broken away forpurposes of clarity;

FIG. 3 is a sectional view of an enlarged scale taken along the line 3-3of FIG. 2 showing the jaw members in full open position;

FIG. 3a is a fragmentary elevational view on an enlarged scale showing aportion of the jaw members in a full closed position;

FIG. 4 is an exploded perspective view of the preorifice capsule viewedfrom the forward end of the spray gun;

FIG. 5 is a sectional view of the spray tip and preorifice capsulesimilar to FIG. 2 but on a greatly enlarged scale; and

FIG. 6 is a sectional view through a pre-orifice capsule showing anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, an airlessspray gun It) is shown. I

The spray gun includes a handle portion 12, a forwardly extending stockportion 14 and a spray portion 16 which is secured to the stock portion14 by means of a bolt 18. In accordance with the present invention, anadjustable pre-orifice spray assembly 20 is fixed to the forward end ofthe spray portion 16.

The liquid to be sprayed is introduced into the spray gun through acombined swivel fitting and strainer holder 22 which is threadedlyconnected to the spray portion 16 of the gun. The fitting 22 is adaptedto be connected to a source of liquid under pressure (not shown) and theliquid is delivered to the internal portions of the gun through apassageway 22a extending through the fitting.

The liquid to be sprayed may be pressurized in any conventional mannerand a supply hose (not shown) leading to the fitting 22 may be branchedif it is desired to use a heater in the supply line. A suitable pump andcirculating system is disclosed in US. Pat. No. 3,018,968 to Levey. Ifno recirculation is required or desired, the fitting 22 may be connectedto a single supply hose leading to a source of liquid under pressure,such as the outlet side of a pump (not shown).

The spray gun 10 also includes a pivoted trigger 24 which is fixed tothe stem of a needle valve 26 for purposes of operating the spray gun.The needle valve 26 and trigger 24 are biased to a forward, non-sprayingposition by conventional means. The spray gun is actuated upon movementof the trigger 24 towards the handle l2 and the corresponding, followingmovement of the needle valve 26 in a rearward direction.

Referring to FIG. 2, the details of the forward portion of the spray gun10 are shown. The adjustable preorifice spray assembly 20 is threadedlyengaged to a cylindrical boss 16a extending from the spray portion I6 ofthe spray gun. The assembly 20 includes an axially fixed, cylindricalmounting sleeve 28 having an internally threaded rearward bore 30 whichthreadedly engages the external threads provided on the cylindrical boss16a. The sleeve 28 has a radially, inwardly extending shoulder 32 whichabuts against the forward end of the boss 16a when the sleeve 28 istightly connected. Alternatively, the spray portion 16 and the sleeve 28may be integrally formed.

The forward end of the sleeve 28 has an internally threaded bore 34which engages an externally threaded nut 36. The nut 36 secures a spraytip or nozzle assembly 38 to the forward end of the spray gun 10. Asealing gasket 360 formed of a suitable seal material such as nylon orteflon is provided at the forward face of the spray tip holder. Thespray tip or nozzle assembly includes a spray tip holder 39 having aflat fan" spray tip 40 mounted therein.

As previously indicated, the liquid to be sprayed is introduced into thegun by means of the fitting 22 and, more particularly, a passageway 22aextending therethrough and communicating with a central bore 42 in thespray portion 16 of the spray gun. The needle valve 26 is axiallymovable with the bore 42, and its movement is guided by a counterbore 44(FIG. 1). The stem of the needle valve extends through the counterbore44 and a gland nut 46 which seals the free, rearward end of thecounterbore.

The forward end of the bore 42 is internally threaded for engagementwith the rearward portion of a cylindrical nut member 48. The forwardportion of the member 48 is threadedly engaged with a valve body holder50. The cylindrical nut member 48 and the valve body holder 50 arerespectively provided with communicating, coaxial internal bores 48a and50a which in turn communicate with the central bore 42 to provide aconduit or passageway through the spray gun for delivcry of liquid tothe spray tip 40.

The forward end of the bore 50a includes a reduced diameter portionhaving a valve body 52 press-fitted therein so that it is secured inplace and sealed against fluid leakage. The valve body 52 is preferablymade of a hard erosion resistant material such as tungsten carbide. Thevalve body 52 has a valve port 54 which provides a flared seatingsurface 56 adjacent the rearward end thereof for sealing, valvingengagement with the rounded end of the needle valve 26.

The forward end of the valve port 54 opens into a pre-orifice capsule 58having a coaxially extending passageway therethrough including anadjustable preorifice 60. The passageway through the pre-orifice capsule58 communicates with the spray tip 40 for delivery thereto of the liquidto be sprayed as described in greater detail below.

Referring to FIGS. 3 through 5, the pre-orifice capsule 58 includes asits principal parts a forward capsule half member 62, a pair ofrelatively movable jaw members 64 and 66, a pair of biasing springs 68and 70, and a rearward capsule half member 72. When the preorificecapsule is assembled, the capsule half member 62, 72 are interlockedtogether in an interference tit and they cooperate to contain thesprings and jaw members in a fixed axial position. The springs arecompressed in the assembled capsule and they resiliently urge the jawmembers in opposite directions along the diameter of the pre-orificecapsule.

The member 72 has a generally cylindrical configuration including acentral wall 73, a forwardly, axially extending skirt portion 74, and arearwardly, axially extending skirt portion 75. The skirt portion 74 isdivided into four arcuate sections by radially opposed slots 76a, 76band relatively larger, radially off-set slots 78a, 78b.

Each of the arcuate sections of the skirt portion 74 includes aninternal shoulder 80 which cooperates to define an internal recess forpurposes of engaging the member 62. Each of the arcuate sections alsoincludes a reduced diameter or wall portion 82 extending to the forwardsurface of the wall 73. The portions 82 cooperate to define a chamberfor receiving the jaw member 64, 66 and spring members 68, 70.

The jaw members 64, 66 respectively include radially extending camfollowing arms 84, 86 and guide legs 85, 87. When the pre-orificecapsule is assembled, the guide legs of each of the jaw members engageadjacent portions of the other of the jaw members in slidingrelationship as indicated below in greater detail. As best shown in FIG.3, the slots 76a and 76b are dimensioned to receive the cam followingarms 84, 86 and contiguously disposed portions of the legs 85, 87 torotationally fix and stabilize the mounting of the jaw members withinthe pre-orifice capsule.

The jaw members 64, 66 are also respectively provided with guide arms 88and 90. The guide arms are dimensioned to engage the reduced diameterportion 82 of an adjacent arcuate section of the skirt portion 74 whenthe jaw members are in a full open position as shown in FIG. 3.

The jaw members 64, 66 are biased apart to their full open position bythe springs 68 and 70 which comprise double layer leaf springs. Thesprings are mounted within the pre-orifice capsule adjacent the recesses78a, 78b which provide clearance for accommodating the deflection of thesprings upon relative movement of the jaw members toward one another.The springs 68, 70 have an axial dimension corresponding to that of thereduced diameter portion 82 and they are entrapped within the assembledpre-orifice capsule. As shown in FIG. 3, the springs 68, 70 work betweenthe adjacent radially inward surfaces of the guide arms 88, 90 and theadjacent, planar wall portions 82 of the slots 78a, 78b to bias the jawmembers apart.

The forward capsule half member 62 includes an axially extendingalignment boss 94, a disc portion 96 and an axially rearward extending,centrally disposed sealing boss 98 projecting from the rearward surfaceof the disc portion 96 (FIG. 5). The sealing boss 98 may be integrallyformed with disc portion 96 as shown or it may be provided by apress-fitted or otherwise bonded insert (not shown) received within abore provided in the disc portion and extending beyond the rear surfacethereof.

The disc portion 96 is dimensioned to be received against the shouldersand to provide an interference fit with the overlying skirt portion 74of the member 72 in order to lock the capsule halves together when theyare assembled. In the assembled condition, the disc portion 96cooperates with the reduced diameter portion 82 and the forward face ofthe central wall 73 to define a chamber having the jaw members andspring members axially contained therein.

The rearwardly extending skirt portion 75 of the member 72 defines arecess 102 dimensioned to receive a forward shoulder of the valve bodyholder 50 (FIG. 2). The base of the recess 102 is defined by therearward face of the central wall 73 of the member 72.

A pair ofthreaded bores 103 extend through the central wall 73 at spacedlocations clear of the springs 68, 70 and the jaws 64, 66. The bores 103are employed in a screw-jacking operation to separate the assembledcapsule half members 62, 72 after the pre-orifice assembly 58 has beenremoved from the spray gun. More particularly, screw members (not shown)are threadedly advanced through the bores 103 and against the adjacent,rearward face of the disc portion 96 to separate the capsule halfmembers.

The forward face of the wall 73 includes a centrally located, axiallyprojecting sealing boss 104 which cooperates with the sealing boss 98 tofacilitate the provision of a fluid seal with the jaw members 64, 66.The boss 104 surrounds the forward end of a passageway 106 which extendsthrough the wall 73 and communicates between the valve port 54 and theadjustable preorifice 60.

Upon emerging from the passageway 106, the liquid enters the adjustablepre-orifice 60 which is defined by the overlying central portions of thejaw members 64, 66. The jaw members are formed of a hard erosionresistant material such as tungsten carbide. As described in greaterdetail below, the pre-orifice 60 is coaxially disposed with respect tothe passageway 106 and it remains in coaxial relationship regardless ofthe selected cross-sectional area of the pre-orifice. Further, thecross-sectional area of the passageway 106 is slightly greater than thatof the pre-orifice when the latter is adjusted to its maximumcross-sectional area.

The central portions of the jaw members 64, 66 respectively, include acurved surface portion 108 and 110 and a transversely disposed planarsurface portion 112 and 114. The planar surface portions 112, 114 areprovided along the guide legs 85, 87 as best shown in FIG. 3. Thus, thecentral portions of the jaw members have a generally J-shapedconfiguration with the curved bottom portions of the J configurationsoppositely disposed from one another.

The planar surface portions 112, 114 engage associated planar surfacesprovided by the adjacent jaw member for purposes of guiding the relativemovement of the jaw members toward and away from one another. Thesegments of the planar surface portions which are not engaged forpurposes of guiding the jaw members cooperate with the curved surfaceportions 108, 110 to define the adjustable pre-orifice 60 when the jawmembers are positioned to define a relatively larger pre-orificecross-sectional area.

Referring to FIG. 3a, the jaw members 64, 66 are shown in a fully closedor minimum pre-orifice area position wherein the curved surface portions108, 110 completely define the pre-orifice 60. In this position, thepre-orifice cross-section has a generally elliptical configuration. Thecurved surfaces 108, 110 may be provided with flats adjacent theengaging edges thereof at the extremities of the long dimension or majoraxis of the pre-orifice for wear purposes.

In the full open or maximum pre-orifice area position shown in FIG. 3,the pre-orifice cross-section assumes a somewhat circular configurationwith substantially equal major and minor axes. ln the intermediatepositions of the jaw members between full open and full closed, thepre-orifice is provided with a generally elongated, oval shapedconfiguration with blunted ends adjacent its major dimension. Thisvariation in crosssectional configuration of the pre-orifice is notdetrimental to the pre-orifice function and its effectiveness inproviding uniform atomization of the sprayed liquid.

As indicated above, the pre-orifice 60 is coaxial with the passageway106 and it remains in a coaxial relationship as its cross-sectional areais varied since the jaw members are arranged for corresponding radialmovement in opposite directions toward and away from one another. Tothat end, the relative movement of the jaw members 64, 66 is controlledby the axial positioning of a cylindrical cam member 116 (FIG. 2)provided by the adjustable pre-orifice spray assembly 20.

The cam member 116 includes a beveled cam surface 118 adjacent itsforward end which is arranged to engage camming surfaces 84a and 860provided by the cam following arms 84, 86 of the jaw members. The cam;member 116 is shown in a fully retracted position in FIG. 2 with thecam surface 118 thereof in nonclosing engagement with the cam surfaces84a, 86a of the jaw members.

The cam member 116 is driven by a drive key 120 extending through a slot122 in the cylindrical mounting sleeve 28. The outer radial portion 120aof the drive key 120 is received within a groove 124 in an adjustmentnut 126 and contained by retainer plate 154 secured to the nut 126. Theadjustment nut 126 has an internally threaded bore 127 which isthreadedly engaged with the axially fixed mounting sleeve 28.Accordingly, upon rotation of the nut 126, it threadedly moves relativeto the sleeve 28 and correspondingly moves the cam member 116 by meansof the drive key 120.

The drive key 120 is provided with a T-shaped configuration wherein thecross member thereof corresponds with the portion 120a and has anarcuate configuration. Thus, a plurality of drive keys and correspondingslots 122 are provided about the periphery of the sleeve 28 in order toassure the smooth axial movement of the cam member 116.

The actual amount of relative movement of the jaw member 64, 66 uponrotation of the adjustment nut 126 is a function of the angle betweenthe cam surface 118 and 84a, 86a together with the pitch of the threads127. ln the illustrated embodiment, each of the jaw members moves aradial distance of about 0.018 inch for each full revolution of theadjustment nut.

As best shown in FIG. 5, the adjustable pre-orifice 60 opens into apassageway 128 provided in the forward capsule half member 62. Thecross-sectional area of the passageway 128 is dimensioned so as to notinterfere with the fluid jet emerging from the pre-orifice 60. Thepassageway 128 includes an enlarged portion 130 which opens into asimilarly dimensioned bore 132 in the spray tip 40. The bore 132preferably has a substantially perpendicular forward end wall 133 andopens into a relatively small diameter bore 134 which leads to the spraytip nozzle opening 136. As the liquid to be sprayed passes through thepre-orifice 60, it is accelerated with a consequent drop in pressure andemitted as a high velocity stream or jet of fluid. The passageway 128and the bore 132 are filled with liquid, and liquid passes through thebore 134 and nozzle opening 136. The high velocity stream or jet ofliquid moves coaxially out of the pre-orifice 60 and travels through thecenter of the passageway 128 and bore 132 as a submerged jet. Thesubmerged jet enters and fills the bore 134 and upon passing through thenozzle opening 136 it is uniformly atomized to provide the desired ovalspray pattern.

When the area of the pre-orifice 60 is equal to the area of the nozzleopening 136, the pressure of the liquid through the pre-orifice dropsfrom the relatively high values in the valve port 54 and passageway 106.The liquid is carried through the bore 134 and the nozzle opening 136 bythe velocity of the submerged fluid jet or kinetic energy thereof, witha relatively small pressure drop, rather than being driven through thenozzle opening by a high pressure-head on the upstream side of thenozzle opening. The liquid in the chamber defined by the passageway 128and bore 132 is at a relatively low static pressure, and the submergedfluid jet travels through the center of this chamber with a relativelyminimum amount of frictional resistance. The quality of atomization isoptimized in this l:l area relation between the pre-orifice and nozzleopening.

The pre-orifice 60 has a sufficient axial length to stabilize the fluidjet as it is formed therein and cause it to persist as a submerged jetuntil it reaches and fills the bore 134 leading to the nozzle opening.It has been found that these objectives are achieved when the preorificeis provided with a minimum axial length equal to from about /2 to about1 times its maximum crosssectional dimension. The pre-orifice may beprovided with a greater relative axial length without significantlyinterfering with the volume of liquid or necessitating excessively highpressures.

The nozzle opening 136 has a conventional flat fan" or cat eyeconfiguration comprising a generally elliptical cross-section with asharp vertices adjacent the ends of its major axis. The cat eyeconfiguration is provided by initially forming the bore 134 as a blindbore terminating in a spherically-shaped end 138. A transverselydisposed V-shaped slot 140 is then cut into the spray tip so as tointersect the spherical end 138 of the bore 134. Thus, the nozzleopening 136 is provided with an elliptically-shaped or elongatedcross-section having a long dimension or major axis no greater than thediameter of the bore 134 and a short dimension or minor axis equal tothe minimum width of the V-slot 140.

As depicted in FIG. 5, the long dimension of the nozzle opening 136 isperpendicular to the plane of the section. Accordingly, the majordimensions of the spray fan emitted from the nozzle opening and theresulting oval shaped spray pattern are also perpendicular to the planeof the section and the spray tip holder 39 is provided with a recess 142to accommodate the full width of the spray fan.

When the pre-orifice 60 is adjusted to a less than full opencross-sectional area, it is necessary to maintain the elongateddimension or major axis thereof is substantially parallel relationshipwith the elongated dimension or major axis of the nozzle opening 136. Inorder to assure the parallel relationship, the alignment boss 94extending from the forward capsule half member 62 is provided with anon-circular cross-section by means of flats 144 extending along itsperipheral surface. The pre-orifice capsule 58 is initially assembledwith the major dimension of the pre-orifice 60 extending in apredetermined direction with respect to the non-circular configurationof the boss 94.

The boss 94 is received within a correspondingly shaped recess 146 in aninsert 148. The insert 148 is press-fitted into a bore 150 in the spraytip holder 39 to prevent relative rotation therebetween. The spray tip40 is similarly press-fitted into the holder 39 so that the majordimension of the nozzle opening 136 extends in a predetermined directionwith respect to the recess 146, and in parallel relationship withrespect to the major dimension of the closed position pre-orifice whenthe boss 94 is received within the recess 146.

The boss 94 is also provided with an axially extending slot 152 whichbisects a portion of the axial extent thereof. The bore 146 isdimensioned to slightly compress the bisected portion of the boss uponinsertion therein, and the slot 152 thereby serves to resiliently lockthe pre-orifice capsule 58 to the spray nozzle assembly 38. A washerseal 153 is disposed about the boss 94 between the spray tip holder 39and the central disc portion 96 of the member 62 to prevent liquid fromescaping between the pre-orifice capsule and holder. The washer seal isformed of a suitable seal material such as teflon or nylon.

If an operator desires to rotate the major dimensions of the spray fanand the oval shaped spray pattern relative to the spray gun 10, it issimply necessary to loosen the nut 36 and rotate the spray nozzleassembly 38 by grasping it adjacent its forward end. Upon rotation ofthe spray nozzle assembly 38, the pre-orifice capsule 58 iscorrespondingly rotated about the forward shoulder of the valve bodyholder 50 and the parallel relationship between the major dimensions ofthe pre-orifice 60 and nozzle opening 136 is maintained. Accordingly, aconventional spray tip and nozzle assembly may be modified to provide aunitized assembly with the preorifice capsule and to assure themaintenance of the desired parallel relationship.

The range of cross-sectional pre-orifice areas through which thepre-orifice is adjustable may be selected on the basis of particularspray applications. The pre-orifice 60 is provided with a minordimension of 0.009 inch and a major dimension of 0.035 inch when the jawmembers 64, 66 are moved to the minimum area or full closed position asshown in FIG. 3a, and the pre-orifice has an equivalent area value equalto about that of a circle of 0.01 l of an inch in diameter. When the jawmembers are moved to the maximum area or full open position as shown inFIG. 2, the minor and major dimensions of the pre-orifice 60 are eachequal to about 0.035 inch. and the pre-orifice has an equivalent areaapproximately equal to that of a circle of 0.035 of an inch in diameter.

Thus, the ratio of the cross-sectional area of the preorifice to thecross-sectional area of the nozzle opening may be varied from one-fourthto two for fine finishing spray tips and a restricted volume andmodified spray pattern is obtainable for most commercially availablespray tips by reducing the ratio value to about L0 or less. When thearea of the pre-orifice is less than that of the nozzle opening, uniformatomization and distribution is still obtained but a lesser volume ofliquid is delivered through the nozzle than would otherwise be obtainedat a given liquid pressure. Although the delivered liquid volume isreduced in this instance, the liquid velocity remains the same, and theresulting spray pattern applied to work surface can be narrowed withoutloss of quality or film thickness by manually bringing the spray guncloser to the work surface.

If the area of the pre-orifice is reduced too much, the jet or liquiddelivered to the bore 134 is insufficient to fill the same and thedesired atomization is not obtainable. The critical limit is believed tobe reached when the area of the pre-orifice is about V4 the area of thenozzle opening.

Ratios in excess of 2.0 are available to provide full spray anglepotential for most spray tips commonly employed. It should beappreciated that uniform atomization is obtained at ratios of about 2.0or when the preorifice area is twice that of the nozzle opening but thata compromise in atomization quality is made when the ratio exceeds 2.0in order to obtain high volume and high speed spraying.

Referring to FIG. 6, a modified embodiment of the pre-orifice capsule isshown. For purposes of convenience, the parts of the modified embodimenthave been designated with the same numbers as the corresponding parts ofthe embodiment shown in FIGS. 1 through 5 but for the addition of primedesignations.

In FIG. 6, the pre-orifice capsule 58' includes as its major elements aforward capsule half member 62, rel atively movable jaw members 64, 66'and a rearward capsule half member 72'. As in the first embodiment, thejaw members 64, 66' cooperate to define an adjustable pre-orifice andthe adjustment thereof is controlled in the same manner as describedabove with respect to the first embodiment.

The capsule half member 72' includes a central wall 73' which isprovided with a passageway 106' extending therethrough. The wall 73' hasa centrally disposed, circular recess which is sized to receive acompression disc insert 172 in sliding relationship. The disc insert 172includes a bore 173 which is coaxial with the passageway 106.

The disc insert 172 projects beyond the forward surface of the wall 73and into sealing engagement with the jaw members 64, 66. The insert 172is axially biased in a forward direction into engagement with the jawmembers by means of a belleville spring 174 disposed between the insertand the bottom of the recess 170. The belleville spring has a generallycircular configuration and it includes a central bore 176 extendingtherethrough.

The forward capsule half member 62' includes a disc portion 96 having acentrally disposed recess 178 in the rearward face thereof whichcommunicates with a passageway 128 extending through a forward alignmentmember 94'. A circular insert 180 is bonded and axially fixed within therecess 178. The insert 180 has a central bore 182 which communicatesbetween the adjustable pre-orifice 60 and the passageway 128'.

The insert 180 projects axially beyond the rearward surface of the discportion 96' of the member 62 and into sealing engagement with the jawmembers 64', 66'. Accordingly, the compression disc insert 172 and theinsert 180 cooperate to engage the jaw members in a fluid sealingarrangement similar to that provided by the sealing bosses 96 and 104.However. the provision of the fluid seal is facilitated by the use ofthe belleville spring 174 to bias the disc insert l72,jaw members 64',66' and the insert 180 into sealing relationship.

While preferred embodiments of the invention have been described inconsiderable detail, it will be understood that various rearrangementsand modifications may be resorted to without departing from the scope ofthe invention as defined in the following claims.

What is claimed is:

1. An airless paint spray gun comprising a body portion having a conduitadapted to be connected at its inlet end to a source of liquid paintunder pressure and adapted to have a spray tip connected to thedischarge end thereof, a pre-orifice assembly adjacent the discharge endof said conduit including relatively movable members definingtherebetween a pre-orifice opening, and manually operable means carriedby said body portion operably connected to said relatively movablemembers and movable to vary the area of said preorifice opening.

2. An airless paint spray gun as set forth in claim 1 wherein saidrelatively movable members are arranged for reciprocable movement towardand away from each other to vary the area of said pre-orifice openingdefined therebetween.

3. An airless paint spray gun as set forth in claim 2 wherein saidpre-orifice assembly includes biasing means and cam following means toprovide said recip rocable movement of said relatively movable membersin opposite radial directions with respect to the axial flow of liquidpaint within said conduit.

4. An airless paint spray gun as set forth in claim 3 wherein saidbiasing means comprise spring means arranged to urge said relativelymovable members apart and said cam following means comprise radiallyextending cam following arms arranged to move said relatively movablemembers together upon engagement with an axially movable camming memberoperably connected to said manually operable means.

5. An airless paint spray gun as set forth in claim 4 wherein saidmanually operably means comprise a control member externally mounted onsaid body portion for threadedly advancing said axially movable cammingmember.

6. An airless paint spray gun as set forth in claim 1 wherein saidpre-orifice assembly comprises interfitted first and second capsulemembers which cooperate to support said relatively movable members andto restrain them against axial movement with respect to the axial flowof liquid paint within said conduit.

7. An airless paint spray gun as set forth in claim 6 wherein saidrelatively movable members are supported within a cavity defined by saidcapsule members.

8. An airless paint spray gun as set forth in claim 1 wherein saidpre-orifice opening has an elongated cross-section including a majororifice dimension extending in a direction substantially perpendicularto the axial flow of liquid paint within said conduit.

9. An airless paint spray gun as set forth in claim 8 wherein saidpre-orifice opening has an axial length at least equal to one-half saidmajor dimension of said elongated cross-section.

10. An airless paint spray gun as set forth in claim 1 wherein saidpre-orifice opening has a generally elliptical cross-section when saidrelatively movable members are moved to a minimum area position.

11. An airless paint spray gun comprising a conduit adapted to beconnected to a source of paint under pressure, a spray tip having anelongated spray opening connected to said conduit, an adjustablepre-orifice in said conduit upstream from said spray opening, saidpre-orifice including opposed surfaces movable toward and away from eachother, said surfaces in one position defining an elongated pre-orificewith its long axis substantially parallel to the long axis of said sprayopening and being movable away from each other to increase the area ofsaid pre-orifice.

12. An airless paint spray gun as set forth in claim 11 wherein saidarea of said pre-orifice opening is adjustable in size from a valueequal to from about one-fourth to about twice the area of said elongatedspray opening.

13. An airless paint spray gun as set forth in claim 11 wherein saidsurfaces are provided by relatively movable members arranged forreciprocable movement toward and away from each other.

14. An airless paint spray gun as set forth in claim 13 wherein saidadjustable pre-orfice includes biasing means and cam following means toprovide said reciprocable movement of said relatively movable members.

15. An airless paint spray gun as set forth in claim 13 wherein saidrelatively movable members are mounted within pre-orifice assembly, saidspray tip and said preorifice assembly including interfittingorientation surfaces for maintaining said long axes of said elongatedspray opening and said pre-orifice opening in said substantiallyparallel relationship.

16. An airless paint spray gun as set forth in claim 15 wherein saidrelatively movable members are sealed within said pre-orifce assembly bya spring biased means.

17. In an airless paint spray gun comprising a body portion having aconduit adapted to be connected at its inlet end to a source of liquidunder pressure and adapted to have a spray tip providing an elongatedspray opening connected to the discharge end thereof the improvementcomprising an adjustable pre-orifice assembly in said conduit upstreamfrom said spray opening, said pre-orifice assembly including relativelymovable surfaces defining therebetween a pre-orifice opening coaxiallydisposed with respect to said spray opening, and said relatively movablesurfaces being movable to vary the area of said pre-orifice opening.

18. The pre-orifice assembly as set forth in claim 17 wherein saidrelatively movable surfaces are arranged for reciprocable movement tovary the area of said preorifice opening.

19. The pre-orifice assembly as set forth in claim 18 wherein saidpre-orifice assembly includes resilient biasing means and cam followingmeans to provide said reciprocable movement.

20. The pre-orifice assembly as set forth in claim 19 wherein saidresilient biasing means comprise spring means operably connected to biassaid relatively movable surfaces apart and said cam following meanscomprise cam following arms operably connected to move said relativelymovable surfaces together.

21. The pre-orifice assembly as set forth in claim wherein saidrelatively movable surfaces are supported within a cavity defined bysaid pre-orifice assembly.

22. The pre-orifice assembly as set forth in claim 21 wherein saidspring means are mounted within said cavity and said cam following armsradially extend from said cavity for engagement with an axially movablecamming member.

23. The pre-orifice assembly as set forth in claim 17 wherein saidpre-orifice opening has an elongated cross-section in at least oneposition of said relatively movable surfaces, and said pre-orificeassembly in cludes alignment means for engaging a spray tip connected tothe discharge end of said conduit and maintaining the long axis of saidpre-orifice opening in substantially parallel relationship with the longaxis of the spray opening.

24. The pre-orfice assembly as set forth in claim 23 wherein saidrelatively movable surfaces include opposed, relatively movable curvedsurface portions which cooperate to provide said pre-orifice openingwith a generally elliptical shaped cross-section in said one position ofsaid relatively movable surfaces.

25. The pre-orifice assembly as set forth in claim 24 wherein saidrelatively movable surfaces include substantially planar surfaceportions transversely disposed with respect to said curved surfaceportions, said relatively movable surfaces being arranged to engage oneanother along segments of said planar surface portions upon relativemovement therebetween, the remaining segments of said planar surfaceportions cooperating with said curved surface portions to define saidpreorifice opening.

26. An airless paint spray gun comprising a body portion with a passagefor paint under pressure, a flat fan spray tip having an elongated sprayopening adapted to be secured to said body portion in communication withthe outlet end of said passage, said body portion having a non-circularelongated pro-orifice in said passage upstream from said spray tip, andinterfitting orientation surfaces on said spray tip and said bodyportion maintaining the long axes of said pre-orifice and said spray.opening in parallel relation.

spray tip.

30. An airless paint spray gun as set forth in claim 29 wherein saidaxially projecting member is frictionally locked within said recess.

31. in an airless spray gun comprising a body portion with a passage ofliquid paint adapted to be connected at its inlet end to a sourceofliquid paint under pressure and adapted to have a flat fan spray tiphaving an elongated spray opening connected to the discharge end of saidconduit, the improvement comprising a pre-orifice assembly defining anon-circular pre-orifice opening upstream in said passage from saidspray tip, and interfitting orientation surfaces on said spray tip andsaid pro-orifice assembly maintaining the long axes of said sprayopening and said pre-orifice opening in parallel relation.

32. The improvement set forth in claim 31 wherein said pre-orificeassembly includes an axially projecting member having a non-circularcross-section received within a recess in said spray tip, and saidinterfitting surfaces are provided by said projecting member and saidrecess.

33. The improvement set forth in claim 32 wherein said projecting memberhas a generally cylindrical shape including at least one axiallyextending flat along its exterior surface.

34. The improvement set forth in claim 32 wherein said projecting memberincludes resilient biasing means for maintaining said projecting memberwithin said recess.

35. The improvement set forth in claim 31 wherein the area of saidpre-orifice opening is variable.

36. The improvement set forth in claim 31 wherein locking means areprovided for maintaining said preorifice assembly and said spray tip isa predetermined axial relationship.

37. The improvement set forth in claim 36 wherein said interfittingsurfaces and said locking means are provided by an axially projectingmember having a non-circular cross-section extending from saidpreorifice assembly and received within a recess in said spray tip.

38. The improvement set forth in claim 37 wherein said resilient biasingmeans comprise an axially extending slot bisecting at least a portion ofthe axial length of said axially projecting member received within saidrecess, said recess being sized to compress and resiliently lock saidbisected portion within said recess.

39. An airless paint spray gun comprising a body portion having aconduit adapted to be connected at its inlet end to a source of liquidpaint under pressure and adapted to have a flat fan spray tip having anelongated spray opening connected to the discharge end of said conduit,said body portion having a non-circular elongated pre-orifice opening insaid conduit upstream from said spray tip, said spray opening having amajor opening dimension extending in a first direction and saidpre-orifice having a major orifice dimension extending in a seconddirection, and said first and second directions being disposed insubstantially parallel relationship.

40. An airless paint spray gun comprising a body portion having aconduit adapted to be connected at its inlet end to a source of liquidpaint under pressure and adapted to have a spray tip connected to thedischarge end thereof, a pre-orifice assembly adjacent the discharge endof said conduit including an axially extending pre-orifice openingadjustable in cross-sectional area, and manually operable means carriedby said body portion operably associated with said pre-orifice assemblyand movable to vary the area of said preorifice opening.

UNITED STATES PATENT OFFICE CER'lt -IFICATE 0F CORRECTION \t PATENT NO.3,865,314

DATED February 11, 1975 mvmroerst Gustave S. Levey and Edward Moser Itis certified that error appears in the ab0ve identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, line 31, after the word "in" insert a Column 4, line 39,"with" should read within Column 8, line 48, delete the word "a".

Column 9, line 3, '"is" should read in Column 9, line 63, after the word"area" insert value Column 10, line 15, "or" should read of Column ll,line 47, "operably" should read operable Column 12, line 33, after"within" insert a Column 14, line 25, "is" should read in Jigned andsealed this 1st day of July 1975.

(31x1) Attest:

C. I'ZfillSl-TALL DANN RUTH C. IZASOt-t Commissioner of Patentsattesting Officer and Trademarks

1. An airless paint spray gun comprising a body portion having a conduitadapted to be connected at its inlet end to a source of liquid paintunder pressure and adapted to have a spray tip connected to thedischarge end thereof, a pre-orifice assembly adjacent the discharge endof said conduit including relatively movable members definingtherebetween a pre-orifice opening, and manually operable means carriedby said body portion operably connected to said relatively movablemembers and movable to vary the area of said pre-orifice opening.
 2. Anairless paint spray gun as set forth in claim 1 wherein said relativelymovable members are arranged for reciprocable movement toward and awayfrom each other to vary the area of said pre-orifice opening definedtherebetween.
 3. An airless paint spray gun as set forth in claim 2wherein said pre-orifice assembly includes biasing means and camfollowing means to provide said reciprocable movement of said relativelymovable members in opposite radial directions with respect to the axialflow of liquid paint within said conduit.
 4. An airless paint spray gunas set forth in claim 3 wherein said biasing means comprise spring meansarranged to urge said relatively movable members apart and said camfollowing means comprise radially extending cam following arms arrangedto move said relatively movable members together upon engagement with anaxially movable camming member operably connected to said manuallyoperable means.
 5. An airless paint spray gun as set forth in claim 4wherein said manually operably means comprise a control memberexternally mounted on said body portion for threadedly advancing saidaxially movable camming member.
 6. An airless paint spray gun as setforth in claim 1 wherein said pre-orifice assembly comprises interfittedfirst and second capsule members which cooperate to support saidrelatively movable members and to restrain them against axial movementwith respect to the axial flow of liquid paint within said conduit. 7.An airless paint spray gun as set forth in claim 6 wherein saidrelatively movable members are supported within a cavity defined by saidcapsule members.
 8. An airless paint spray gun as set forth in claim 1wherein said pre-orifice opening has an elongated cross-sectionincluding a major orifice dimension extending in a directionsubstantially perpendicular to the axial flow of liquid paint withinsaid conduit.
 9. An airless paint spray gun as set forth in claim 8wherein said pre-orifice opening has an axial length at least equal toone-half said major dimension of said elongated cross-section.
 10. Anairless paint spray gun as set forth in claim 1 wherEin said pre-orificeopening has a generally elliptical cross-section when said relativelymovable members are moved to a minimum area position.
 11. An airlesspaint spray gun comprising a conduit adapted to be connected to a sourceof paint under pressure, a spray tip having an elongated spray openingconnected to said conduit, an adjustable pre-orifice in said conduitupstream from said spray opening, said pre-orifice including opposedsurfaces movable toward and away from each other, said surfaces in oneposition defining an elongated pre-orifice with its long axissubstantially parallel to the long axis of said spray opening and beingmovable away from each other to increase the area of said pre-orifice.12. An airless paint spray gun as set forth in claim 11 wherein saidarea of said pre-orifice opening is adjustable in size from a valueequal to from about one-fourth to about twice the area of said elongatedspray opening.
 13. An airless paint spray gun as set forth in claim 11wherein said surfaces are provided by relatively movable membersarranged for reciprocable movement toward and away from each other. 14.An airless paint spray gun as set forth in claim 13 wherein saidadjustable pre-orfice includes biasing means and cam following means toprovide said reciprocable movement of said relatively movable members.15. An airless paint spray gun as set forth in claim 13 wherein saidrelatively movable members are mounted within pre-orifice assembly, saidspray tip and said pre-orifice assembly including interfittingorientation surfaces for maintaining said long axes of said elongatedspray opening and said pre-orifice opening in said substantiallyparallel relationship.
 16. An airless paint spray gun as set forth inclaim 15 wherein said relatively movable members are sealed within saidpre-orifce assembly by a spring biased means.
 17. In an airless paintspray gun comprising a body portion having a conduit adapted to beconnected at its inlet end to a source of liquid under pressure andadapted to have a spray tip providing an elongated spray openingconnected to the discharge end thereof the improvement comprising anadjustable pre-orifice assembly in said conduit upstream from said sprayopening, said pre-orifice assembly including relatively movable surfacesdefining therebetween a pre-orifice opening coaxially disposed withrespect to said spray opening, and said relatively movable surfacesbeing movable to vary the area of said pre-orifice opening.
 18. Thepre-orifice assembly as set forth in claim 17 wherein said relativelymovable surfaces are arranged for reciprocable movement to vary the areaof said pre-orifice opening.
 19. The pre-orifice assembly as set forthin claim 18 wherein said pre-orifice assembly includes resilient biasingmeans and cam following means to provide said reciprocable movement. 20.The pre-orifice assembly as set forth in claim 19 wherein said resilientbiasing means comprise spring means operably connected to bias saidrelatively movable surfaces apart and said cam following means comprisecam following arms operably connected to move said relatively movablesurfaces together.
 21. The pre-orifice assembly as set forth in claim 20wherein said relatively movable surfaces are supported within a cavitydefined by said pre-orifice assembly.
 22. The pre-orifice assembly asset forth in claim 21 wherein said spring means are mounted within saidcavity and said cam following arms radially extend from said cavity forengagement with an axially movable camming member.
 23. The pre-orificeassembly as set forth in claim 17 wherein said pre-orifice opening hasan elongated cross-section in at least one position of said relativelymovable surfaces, and said pre-orifice assembly includes alignment meansfor engaging a spray tip connected to the discharge end of said conduitand maintaining the long axis of said pre-orifice opening insubstantially parallel relationship with the long axis of the sprayopening.
 24. The pre-orfice assembly as set forth in claim 23 whereinsaid relatively movable surfaces include opposed, relatively movablecurved surface portions which cooperate to provide said pre-orificeopening with a generally elliptical shaped cross-section in said oneposition of said relatively movable surfaces.
 25. The pre-orificeassembly as set forth in claim 24 wherein said relatively movablesurfaces include substantially planar surface portions transverselydisposed with respect to said curved surface portions, said relativelymovable surfaces being arranged to engage one another along segments ofsaid planar surface portions upon relative movement therebetween, theremaining segments of said planar surface portions cooperating with saidcurved surface portions to define said pre-orifice opening.
 26. Anairless paint spray gun comprising a body portion with a passage forpaint under pressure, a flat fan spray tip having an elongated sprayopening adapted to be secured to said body portion in communication withthe outlet end of said passage, said body portion having a non-circularelongated pre-orifice in said passage upstream from said spray tip, andinterfitting orientation surfaces on said spray tip and said bodyportion maintaining the long axes of said pre-orifice and said sprayopening in parallel relation.
 27. An airless paint spray gun as setforth in claim 26 wherein said interfitting orientation surfaces areprovided by an axially projecting member extending between said bodyportion and said spray tip.
 28. An airless paint spray gun as set forthin claim 27 wherein said axially projecting member has a non-circularcross-section.
 29. An airless paint spray gun as set forth in claim 28wherein said axially projecting member is fixed to said body portion andextends into a recess provided by said spray tip.
 30. An airless paintspray gun as set forth in claim 29 wherein said axially projectingmember is frictionally locked within said recess.
 31. In an airlessspray gun comprising a body portion with a passage of liquid paintadapted to be connected at its inlet end to a source of liquid paintunder pressure and adapted to have a flat fan spray tip having anelongated spray opening connected to the discharge end of said conduit,the improvement comprising a pre-orifice assembly defining anon-circular pre-orifice opening upstream in said passage from saidspray tip, and interfitting orientation surfaces on said spray tip andsaid pre-orifice assembly maintaining the long axes of said sprayopening and said pre-orifice opening in parallel relation.
 32. Theimprovement set forth in claim 31 wherein said pre-orifice assemblyincludes an axially projecting member having a non-circularcross-section received within a recess in said spray tip, and saidinterfitting surfaces are provided by said projecting member and saidrecess.
 33. The improvement set forth in claim 32 wherein saidprojecting member has a generally cylindrical shape including at leastone axially extending flat along its exterior surface.
 34. Theimprovement set forth in claim 32 wherein said projecting memberincludes resilient biasing means for maintaining said projecting memberwithin said recess.
 35. The improvement set forth in claim 31 whereinthe area of said pre-orifice opening is variable.
 36. The improvementset forth in claim 31 wherein locking means are provided for maintainingsaid pre-orifice assembly and said spray tip is a predetermined axialrelationship.
 37. The improvement set forth in claim 36 wherein saidinterfitting surfaces and said locking means are provided by an axiallyprojecting member having a non-circular cross-section extending fromsaid pre-orifice assembly and received within a recess in said spraytip.
 38. The improvement set forth in claim 37 wherein said resilientbiasing means comprise an axially extending slot bisecting at least aportion of the axial length of said axially projecting member receivedwithin sAid recess, said recess being sized to compress and resilientlylock said bisected portion within said recess.
 39. An airless paintspray gun comprising a body portion having a conduit adapted to beconnected at its inlet end to a source of liquid paint under pressureand adapted to have a flat fan spray tip having an elongated sprayopening connected to the discharge end of said conduit, said bodyportion having a non-circular elongated pre-orifice opening in saidconduit upstream from said spray tip, said spray opening having a majoropening dimension extending in a first direction and said pre-orificehaving a major orifice dimension extending in a second direction, andsaid first and second directions being disposed in substantiallyparallel relationship.
 40. An airless paint spray gun comprising a bodyportion having a conduit adapted to be connected at its inlet end to asource of liquid paint under pressure and adapted to have a spray tipconnected to the discharge end thereof, a pre-orifice assembly adjacentthe discharge end of said conduit including an axially extendingpre-orifice opening adjustable in cross-sectional area, and manuallyoperable means carried by said body portion operably associated withsaid pre-orifice assembly and movable to vary the area of saidpre-orifice opening.